The intention of the help page was to explain that the OID strings (like "1.2.840.113549.3.7") are acceptable as encryptionAlgorithm argument, but it looks like this was not clear enough.
Additionally, algorithm name ("TripleDES", "RC2", ...) or type (typeof(System.Security.Cryptography.TripleDES), ...) is accepted as well.
We will update the help page (and the documentation file) to clearly state this, thanks for letting us know!
Update: The documentation has been updated in the current release of Rebex SFTP and SSH Shell.